Hmm, that's annoying lol.
I take it this is a pre-X reg HDi? If so, most squeal when the lift pump primes, but not usually that loudly tbf! I'd check the fuel filter personally, check it's clean/clear and that the pipes to it aren't laying against anything else or kinked at all, its them vibrating that causes the whine I believe.
It's not the HP pump as that is driven by the cambelt so not moving until you turn the engine over.
I take it this is a pre-X reg HDi? If so, most squeal when the lift pump primes, but not usually that loudly tbf! I'd check the fuel filter personally, check it's clean/clear and that the pipes to it aren't laying against anything else or kinked at all, its them vibrating that causes the whine I believe.
It's not the HP pump as that is driven by the cambelt so not moving until you turn the engine over.